1. Field of the Invention
This invention relates to a straddle-type vehicle having a cooling structure of a rear wheel brake device that applies brake with fluid pressure of brake fluid.
2. Description of Related Art
In a straddle-type vehicle such as a motorcycle, a disk brake is conventionally used because, for example, the brake force is easy to control, and the cooling efficiency is good as the brake calipers and the disk are exposed outside, so that drive-induced airflow strikes them directly.
However, as for a scooter type motorcycle with its disk brake covered with a vehicle body cover, the drive-induced airflow is less likely to directly strike the brake calipers and the disk, possibly resulting in poor cooling efficiency. Therefore, it is preferable to provide a drive-induced airflow introducing port in the vehicle body cover to introduce drive-induced airflow to the brake calipers and others to improve cooling efficiency.
A scooter type motorcycle with a rear wheel brake device is described in Japanese Patent Document JP-B-3010221. In page 4, lines 15-24, JP-B-3010221 discloses a drive-induced airflow introducing port formed in a position on the vehicle body cover, in front of the rear wheel brake device, and beside the front part of the engine unit. The vehicle body cover is further formed with a recess receding toward the inside of the vehicle body in a position in front of the drive-induced airflow introducing port to be continuous to the drive-induced airflow introducing port. An airflow introducing member is provided that is continuous from the recess inside the vehicle body cover, along the underline of the vehicle body cover, extending toward the rear of the vehicle body in a straight line in side view, to form an airflow moving passage together with the inside face of the vehicle body cover for guiding the drive-induced airflow from the drive-induced airflow introducing port to the calipers of the rear wheel brake device.
Further, in page 3, line 50 to page 4, line 15, JP-B-3010221 states that the side portion of the side cover is made so that the drive-induced airflow guided from the recess continuing to the drive-induced airflow introducing port flows to the airflow guiding member that guides the drive-induced airflow to the inside of the rear cover in cooperation with the inside surface of the rear cover.
According to the above, in page 4, lines 24-29, JP-B-3010221 states that it is possible to cool the calipers of the rear wheel brake device by utilizing the drive-induced airflow. Moreover, the drive-induced airflow can be guided smoothly to the calipers without bending largely. Further, the airflow guiding member makes it possible to guide the cold drive-induced airflow directly to and cool the calipers without picking up heat of the engine.
However, according to JP-B-3010221, in the case it is intended to blow a larger volume of drive-induced airflow to the brake calipers through the airflow guiding member (drive-induced airflow guiding duct), it is necessary to form a large airflow guiding member, increase sheet thickness of the rear cover (vehicle body cover) to support the airflow guiding member, and use a component of higher strength and larger size for joining it. Therefore, the structure is highly complex, and the number of mechanical parts is increased.
Further, the cooling efficiency of the brake calipers is considered to improve if the guide-out port of the airflow guiding member is provided in a position nearer to the brake calipers.
Because no obstacle to drive-induced airflow is present in the area below the footrest on which the rider's foot is placed and no turbulence in drive-induced airflow occurs there, it is considered that cooling efficiency is improved by forming the drive-induced airflow introducing port below the footrest to cool the brake calipers with the turbulence-free, drive-induced airflow, rather than forming the drive-induced airflow introducing port in a position in front of the rear wheel brake device, beside the front part of the engine unit.